Who killed sutton mercer in the lying game by Sara Shepard?

It says that Sutton watched Emma tell Ethan the whole story, everything. It didn't go through the convoersation so I'm sure Emma told Ethan her name. I think it's too early to tell who killed Sutton. There are too many different possibilities. There's Laurel, Madison & Charolette who all had motives to kill her. Then there's mysterious Ethan. There's the disappered Thayer and Madison's dad who is supposed to be in Hong Kong. There's too many possiblites to tell so soon.

I completely agree with the person above me, it's too early to tell. She probably told him her name while telling the story.

I agree with the two answers above me. It's definitely not Ethan. Emma told Ethan the whole story and the two are trying to figure out Sutton's murder. As said towards the end of book two "This has to end now." (meaning we should tell the cops). I myself don't think it was Laurel, Charlotte, or Madison. I think it was the Twitter Twins according to the clues in book one and two.
It's not the Twitter Twins. As much as they hated Sutton they wouldn't kill her all they wanted was to be in their group. I don't know, but my possibilities are Ethan, Emma's real mom, Madison's dad. Madison's dad cause he's abusive and maybe to get back at Sutton for what she did to Thayer.